Power converter, power supply control method thereof, and power supply control chip

Abstract

The embodiment of the present application provides a power converter and its power supply control method and power control chip, the power converter mainly includes a transformer, a main switch tube, a power control chip, a voltage detection module and a sampling control module, etc. The transformer includes a main winding and an auxiliary winding with the same polarity, and the power control chip includes a charging control module, wherein the sampling control module and the voltage detection module are located inside or outside the power control chip; the first end of the sampling control module is connected to the demagnetization detection pin of the chip, the second end is connected to the first end of the charging control module, and the third end is connected to the negative power pin of the chip; the second end of the charging control module is connected to the voltage detection module, and the third end is connected to the positive power pin of the chip. The solution of the present application can overcome the defect in the prior art that the power supply voltage of the power control chip needs to withstand a higher voltage due to the voltage following of the traditional auxiliary winding, so that the voltage of the chip can be stabilized at the required set value, etc.

Description

Technical Field

[0001] The present application relates to the field of power conversion technology, and in particular to a power converter and a power supply control method thereof and a power supply control chip. Background Art

[0002] A PD power adapter is a power adapter that supports the PD (Power Delivery) protocol. PD power supplies are generally high in power. In order to meet the European Energy Star energy efficiency standards, a quasi-resonant system power control chip is generally used. The output voltage range of PD power supplies is large, and the common output is 3.3V to 20V, that is, there is a phenomenon that the maximum voltage is 6 times the minimum voltage.

[0003] In a conventional flyback converter that uses an auxiliary winding to power the power control chip, the auxiliary winding has the same polarity as the secondary winding. When the turns ratio of the auxiliary winding and the secondary winding is fixed, the voltage of the conventional auxiliary winding when powering the chip is approximately proportional to the output voltage of the flyback converter, that is, the variation range of the power supply voltage will also reach 6 times.

[0004] In order not to affect the efficiency of the power control chip driving the main switch tube, there are currently two common practices on the market. One is to add an external linear voltage regulator circuit (LDO) in front of the power pin of the power control chip to reduce the voltage; the other is to set an LDO module inside the power control chip to provide a stable power supply for the chip. However, the first solution requires adding an LDO on the periphery, which increases the cost and reduces the system efficiency; the second solution requires the use of a higher voltage-resistant process, which increases the chip area, increases the chip heat, and also reduces the system efficiency and system stability, and increases the cost. Therefore, these two methods cannot effectively solve the power supply problem of the main control chip in PD power applications. Summary of the invention

[0005] In view of this, in order to overcome the deficiencies in the prior art, the present application provides a power converter and a power supply control method thereof and a power supply control chip.

[0006] An embodiment of the present application provides a power converter, comprising: a transformer, a main switch tube, a power control chip, a power supply capacitor, a current limiting resistor, a voltage detection module and a sampling control module, wherein the transformer comprises a main winding and an auxiliary winding having the same polarity, the power control chip comprises a demagnetization detection pin, a positive power pin, a negative power pin and a charging control module, and the sampling control module and the voltage detection module are located inside or outside the power control chip;

[0007] The first end of the main winding is used to connect to the input voltage, and the second end is connected to the main switch tube;

[0008] A first end of the auxiliary winding is connected to the demagnetization detection pin, and a second end is grounded;

[0009] The positive pin of the power supply is grounded through the power supply capacitor and is also connected to the first end of the main winding via the current limiting resistor; the negative pin of the power supply is grounded;

[0010] The first end of the sampling control module is connected to the demagnetization detection pin, the second end is connected to the first end of the charging control module, and the third end is connected to the negative power pin;

[0011] The second end of the charging control module is connected to the output end of the voltage detection module, and the third end is connected to the positive electrode pin of the power supply;

[0012] The input end of the voltage detection module is connected to the positive pin of the power supply.

[0013] In one embodiment, the voltage detection module is used to detect the voltage of the positive pin of the power supply, and output a path opening signal when the voltage of the positive pin of the power supply is lower than a preset value;

[0014] The charging control module is used to control the second end of the sampling control module and the positive pin of the power supply to be in a conductive state when receiving the path opening signal;

[0015] Wherein, the charging control module includes a switch unit and a clamping diode, the first end of the switch unit is connected to the second end of the sampling control module, the second end is connected to the clamping diode set in the forward direction, and the third end is connected to the output end of the voltage detection module.

[0016] In one embodiment, the switch unit includes a current source, a voltage drop resistor, a first switch tube and a first switch, the voltage drop resistor is connected in parallel between a control end and a first end of the first switch tube, the first end of the first switch tube is connected to the second end of the sampling control module, the second end is connected to the clamping diode, and the control end is connected to the first end of the first switch;

[0017] The second end of the first switch is connected to the current source, and the control end is connected to the voltage detection module.

[0018] In one embodiment, the first switch tube is a MOS tube or a triode.

[0019] In one embodiment, the sampling control module is used to control the short circuit between the first end and the second end of the sampling control module and the open circuit between the second end and the third end when the main switch tube is turned on after the second end of the sampling control module and the positive power supply pin are in a conductive state, so that the current generated by the auxiliary winding flows from the demagnetization detection pin to the power supply capacitor;

[0020] Wherein, the sampling control module includes a second switch, a third switch and a voltage dividing unit composed of a first resistor and a second resistor connected in series;

[0021] One end of the first resistor is connected to the demagnetization detection pin, and the other end is respectively connected to one end of the second resistor and the first end of the charging control module;

[0022] The second switch is connected in parallel to two ends of the first resistor;

[0023] The other end of the second resistor is connected to one end of the third switch, and the other end of the third switch is connected to the negative power supply pin.

[0024] An embodiment of the present application further provides a power supply control method for a power converter, wherein the power converter adopts the above-mentioned power converter, and the method comprises:

[0025] When it is detected that the voltage of the positive pin of the power supply is lower than a preset value, a path opening signal is generated;

[0026] When the charging control module receives the path opening signal, the second end of the sampling control module and the positive pin of the power supply are controlled to be in a conductive state;

[0027] When the second end of the sampling control module and the positive power supply pin are in a conductive state, when the main switch tube is turned on, the sampling control module controls the first end and the second end of the sampling control module to be short-circuited and the second end and the third end to be open-circuited, so that the current generated by the auxiliary winding flows from the demagnetization detection pin to the power supply capacitor.

[0028] In one embodiment, the power supply control method of the power converter further includes:

[0029] When it is detected that the voltage of the positive pin of the power supply is higher than the preset value, a path shutoff signal is generated;

[0030] When receiving the path shutoff signal, the charging control module controls the conductive state between the second end of the sampling control module and the positive pin of the power supply to be disconnected.

[0031] In one embodiment, the power supply control method of the power converter further includes:

[0032] After the conductive state between the second end of the sampling control module and the positive power supply pin is disconnected, when the main switch tube is turned off, the sampling control module controls the short circuit state between the first end and the second end of the sampling control module to be disconnected and the second end and the third end to be conductive.

[0033] In one embodiment, the sampling control module includes a second switch, a third switch, and a sampling unit composed of a first resistor and a second resistor connected in series, wherein one end of the first resistor is connected to the demagnetization detection pin, and the other end is respectively connected to one end of the second resistor and the first end of the charging control module;

[0034] The second switch is connected in parallel to both ends of the first resistor; the other end of the second resistor is connected to one end of the third switch, and the other end of the third switch is connected to the negative electrode pin of the power supply;

[0035] The method further comprises:

[0036] The sampling unit collects the electrical signal on the demagnetization detection pin to determine the state of the transformer. After the transformer is demagnetized, the resonant current of the transformer in the resonant stage is obtained. The resonant current is used to control the main switch tube to turn on when the resonant current is zero.

[0037] The embodiment of the present application further provides a power control chip, comprising: a demagnetization detection pin, a positive power pin, a negative power pin, a sampling control module, a charging control module and a voltage detection module;

[0038] The demagnetization detection pin is used to connect the auxiliary winding of the transformer in the power converter;

[0039] The positive power supply pin is used to be grounded through a power supply capacitor and is also connected to the main winding of the transformer via a current limiting resistor; the negative power supply pin is used to be grounded; wherein the auxiliary winding has the same polarity as the main winding, and the main winding is connected to the main switch tube in the power converter;

[0040] The first end of the sampling control module is connected to the demagnetization detection pin, the second end is connected to the first end of the charging control module, and the third end is connected to the negative power pin;

[0041] The second end of the charging control module is connected to the output end of the voltage detection module, and the third end is connected to the positive electrode pin of the power supply;

[0042] The input end of the voltage detection module is connected to the positive pin of the power supply.

[0043] The embodiments of the present application have the following beneficial effects:

[0044] The power converter of this embodiment can well overcome the defect in the prior art that the power supply voltage of the power control chip needs to withstand a higher voltage due to the voltage following of the conventional auxiliary winding by setting the auxiliary winding to have the same polarity as the main winding, and at the same time, making the voltage range of the auxiliary winding no longer follow the output voltage of the secondary winding. In addition, this embodiment uses the internal design of the power control chip to realize the circuit structure of internal charging, and even if the traditional LDO and high-loss structure design based on resistor current limiting are abandoned, the voltage of the power control chip can still be stabilized at the required set value. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0046] Figure 1 A schematic diagram of the structure of a flyback converter in which a conventional auxiliary winding supplies power to a power control chip is shown;

[0047] Figure 2 A schematic diagram of a structure in which an external LDO module is used for voltage stabilization in an existing flyback converter is shown;

[0048] Figure 3 A first structural schematic diagram of a power converter according to an embodiment of the present application is shown;

[0049] Figure 4 A second structural schematic diagram of a power converter according to an embodiment of the present application is shown;

[0050] Figure 5 A first flow chart of a power supply control method of a power converter according to an embodiment of the present application is shown;

[0051] Figure 6 A schematic diagram of the structure of a power control chip according to an embodiment of the present application is shown.

[0052] Description of main component symbols:

[0053] 100-power converter; 110-voltage detection module; 130-sampling control module; 120-charging control module; 121-switch unit; C0-filter capacitor; C1-power supply capacitor; C2-output capacitor; C3-absorption capacitor; R1-current limiting resistor; R2-first resistor; R3-second resistor; Rs-current sampling resistor; R4-absorption resistor; R5-voltage drop resistor; U1-power control chip; DEM-demagnetization detection pin; VDD-positive power pin; GND-negative power pin; PWM-drive signal output pin; FB-primary feedback pin; T-transformer; Q1-main switch tube; Q0-first switch tube; S1-first switch; S2-second switch; S3-third switch; D0-first diode; D1-clamping diode; D2-rectifier diode; D3-anti-reverse diode. DETAILED DESCRIPTION

[0054] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0055] The components of the embodiments of the present application generally described and shown in the drawings herein may be arranged and designed in various configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0056] like Figure 1 As shown, for the traditional flyback power converter, its working principle mainly includes: after the AC power is connected, it is rectified by the rectifier bridge, and the filter capacitor C0 performs filtering and energy storage. When the main switch tube Q1 is turned on, the energy is stored at both ends of the primary winding of the transformer T, the current through the primary winding increases linearly, and the magnetic flux in the magnetic core of the transformer T gradually increases; at this time, the secondary winding and the auxiliary winding induce a voltage with the opposite polarity to the primary winding, so that the first diode D0 and the rectifier diode D2 are cut off, and the output capacitor C2 is discharged to provide load current.

[0057] When the main switch Q1 is turned off, the primary winding is open, the polarity of the induced electromotive force of the secondary winding and the auxiliary winding is reversed, D1 and D2 are turned on, and the magnetic flux in the magnetic core of the transformer T begins to be released. Part of the energy is used on the secondary side to charge the capacitor C2 and power the load, and the other part of the energy is used to charge the capacitor C1 and power the power control chip U1 through the auxiliary winding. At this time, the circuit on one side of the primary winding is open, the secondary winding and the auxiliary winding circuit are working, and the polarity of the auxiliary winding and the secondary winding is the same, so it satisfies: Among them, V A and V S are the voltages of the auxiliary winding and the secondary winding, N A and N S are the turns of the auxiliary winding and the secondary winding respectively. Further, it is converted to: Among them, V D is the voltage drop of the diode, V DD is the chip power supply voltage, V out is the output voltage.

[0058] Then, we get: If the voltage drop of the diode is ignored, the above formula can be simplified to: It can be understood that in PD power supply applications, the chip power supply voltage V DD With output voltage V out The variation range will reach 6 times. In order not to affect the efficiency of driving the main switch tube Q1, the output voltage is set to the lowest, V DD The minimum value is 10V, and when the output voltage is switched to 6 times, V DD will reach 60V.

[0059] Obviously, 60V is too high for the power control chip U1. DD If high voltage may occur, the following can be used Figure 2 The solution shown is to set an LDO circuit before the power pin of the power control chip U1. Of course, the LDO circuit can also be set inside the power control chip U1. If it is inside, the power control chip U1 needs to be manufactured using a 60V high-voltage process.

[0060] On the other hand, V DD Such a large voltage variation range will also make the driver design more complicated. In order to protect the power tube gate oxide at V DD In order to prevent breakdown under high voltage, the output voltage needs to be clamped. Generally, a voltage regulator is used to perform this function, which will greatly increase the power consumption of the chip. DD When the voltage is high, the turn-on speed of power devices will be greatly increased, which will lead to a sharp deterioration of EMI. The whole machine solution needs to add additional devices to solve the problems of conduction and radiation, and the cost will further increase. Therefore, simply improving the process withstand voltage cannot solve the pain points of traditional power supply solutions under PD power supply applications.

[0061] To this end, the present application proposes a power converter, which modifies the auxiliary winding of the transformer into a forward power supply so that the voltage range of the auxiliary winding follows the input voltage range of the primary winding, thereby overcoming the defect in the prior art that the power supply voltage of the power control chip needs to withstand a higher voltage because the auxiliary winding voltage follows the output voltage. At the same time, in order to stabilize the working voltage, the internal structure of the power control chip is adjusted accordingly, so that V DD The voltage is stabilized at a certain set point without using high-loss circuit structures such as LDO and resistor current limiting.

[0062] The power converter is described below in conjunction with specific embodiments.

[0063] Example 1

[0064] Please refer to Figure 3 This embodiment provides a power converter 100, which can be applied to various power supply occasions, such as a PD adapter with variable voltage output, and other electronic devices involving power conversion.

[0065] Exemplarily, the power converter 100 includes a transformer T, a main switch tube Q1, a power control chip U1, a power supply capacitor C1, a current limiting resistor R1, a voltage detection module 110 and a sampling control module 130, wherein the transformer T includes a main winding and an auxiliary winding with the same polarity. Typically, the first end of the main winding is used to connect the input voltage, and the second end is connected to the main switch tube Q1, and the main switch tube Q1 is usually connected to the power ground (i.e., grounded) via the current sampling resistor Rs. The voltage detection module 110 and the sampling control module 130 can be located inside or outside the power control chip U1.

[0066] Optionally, an absorption circuit may be provided at both ends of the main winding, for example, Figure 3 As shown, the absorption circuit can be composed of an absorption capacitor C3 and an absorption resistor R4 connected in parallel and then connected in series with an anti-reverse diode D3. In some other embodiments, the power converter 100 also includes: a full-bridge rectifier circuit and a filter capacitor C0, wherein the input end of the full-bridge rectifier circuit is used to access the AC power supply AC, and the output end is used to connect the filter capacitor C0; the positive electrode of the filter capacitor C0 is connected to the opposite end of the main winding, and the negative electrode is grounded. At this time, the voltage output by the filter capacitor C0 is used as the above-mentioned input voltage.

[0067] In this embodiment, the power control chip U1 is used as the main control chip of the main switch tube Q1, and is mainly used to output the corresponding PWM drive signal according to the demand to control the main switch tube Q1 accordingly, so as to achieve the purpose of power conversion. The power converter 100 can also realize the self-starting of the circuit and the self-power supply of the power control chip U1.

[0068] Exemplarily, the power control chip U1 includes a demagnetization detection pin DEM, a positive power pin VDD, and a negative power pin GND, as well as a basic drive signal output pin PWM, a primary feedback pin FB, etc., wherein the drive signal output pin PWM is used to output a PWM signal to control the on and off of the main switch tube Q1. It can be understood that the power control chip U1 of this embodiment mainly adds a new chip self-power supply function without changing the existing functions of the chip.

[0069] For example, Figure 3 As shown, the demagnetization detection pin DEM of the power control chip U1 is connected to the first end of the auxiliary winding, and the second end of the auxiliary winding is grounded; the positive power pin VDD of the power control chip U1 is grounded through a power supply capacitor C1, and is also connected to the first end of the main winding via a current limiting resistor R1. It can be understood that the power supply capacitor C1 is used to store energy to provide the required operating voltage for the power control chip U1 and clamp the voltage required by the chip. The negative power pin GND of the power control chip U1 is grounded. In addition, the signal output pin PWM of the power control chip U1 is connected to the control end of the main switch tube Q1, and the feedback pin is connected to the corresponding primary feedback circuit, etc.

[0070] In one embodiment, if Figure 3 As shown, the power control chip U1 is also provided with a charging control module 120, and a built-in sampling control module 130 and a voltage detection module 110. Exemplarily, the first end of the sampling control module 130 is connected to the demagnetization detection pin DEM, the second end is connected to the first end of the charging control module 120, and the third end is connected to the negative power pin GND; the second end of the charging control module 120 is connected to the voltage detection module 110, and the third end is connected to the positive power pin VDD; and the voltage detection module 110 is connected to the positive power pin VDD. It is worth noting that the above-mentioned sampling control module 130 and voltage detection module 110 can be located inside the power control chip U1, or outside the chip, which is not limited here. This embodiment is mainly described with the built-in solution.

[0071] The voltage detection module 110 is used to detect the voltage of the positive power pin VDD, and when the voltage of the positive power pin VDD is lower than a preset value, a path opening signal is output to the charging control module 120. In addition, the voltage detection module 110 is also used to output a path closing signal when the voltage of the positive power pin VDD is higher than the preset value.

[0072] For example, the voltage detection module 110 may be composed of a plurality of voltage-dividing resistors and a voltage comparator, wherein the voltage-dividing resistor is mainly used to detect the voltage value, and the voltage comparator is used to compare the detected voltage value with a preset value and output the comparison result. For example, a high level of the output indicates a path-on signal, and a low level indicates a path-off signal.

[0073] The charging control module 120 is mainly used to control the second end of the sampling control module 130 and the positive power supply pin VDD to be in a conductive state when receiving the start signal, that is, when current flows, the current can generate a voltage drop to turn on the switch tube, thereby allowing the current to flow from the second end through the charging control module 120 to the positive power supply pin VDD.

[0074] On the contrary, when the voltage of the positive power pin VDD is higher than the preset value, the conductive state between the second end of the sampling control module 130 and the positive power pin VDD is disconnected. At this time, even if current is input to the second end, the current cannot flow to the positive power pin VDD.

[0075] For example, Figure 4 As shown, the charging control module 120 includes a switch unit 121 and a clamping diode D1, wherein a first end of the switch unit 121 is connected to a second end of the sampling control module 130, a second end is connected to a forward-set clamping diode D1, and a third end is connected to an output end of the voltage detection module 110.

[0076] In one embodiment, the switch unit 121 may include a current source I1, a voltage drop resistor R5, a first switch tube Q0 and a first switch S1, wherein the voltage drop resistor R5 is connected in parallel between the control end and the first end of the first switch tube Q0, the first end of the first switch tube Q0 is connected to the second end of the sampling control module 130, the second end is connected to the clamping diode D1, and the control end is connected to the first end of the first switch S1; the second end of the first switch S1 is connected to the current source, and the control end is connected to the voltage detection module 110.

[0077] It can be understood that the above-mentioned current source is mainly used to provide a bias power supply for the first switch tube Q0, so that when the first end of the first switch tube Q0 is connected to the current, a voltage drop can be formed, thereby turning on the first switch tube Q0. For example, the first switch tube Q0 can be a MOS tube or a triode. Taking a PMOS tube as an example, the gate of the PMOS tube is the control end, and the source and drain are respectively the above-mentioned first end and second end.

[0078] The sampling control module 130 is used to control the first end and the second end of the sampling control module 130 to be short-circuited and the second end and the third end to be open-circuited when the second end of the sampling control module 130 and the positive power supply pin VDD are in a conductive state and the main switch tube Q1 is turned on. At this time, the first switch tube Q0 in the above-mentioned switch unit 121 is turned on, so that the current generated by the auxiliary winding flows from the demagnetization detection pin DEM to the positive power supply pin VDD, thereby charging the power supply capacitor C1.

[0079] In one embodiment, if Figure 4 As shown, the sampling control module 130 includes a second switch S2, a third switch S3, and a sampling unit composed of a first resistor R2 and a second resistor R3 connected in series, wherein one end of the first resistor R2 is connected to the demagnetization detection pin DEM, and the other end is respectively connected to one end of the second resistor R3 and the first end of the charging control module 120; the second switch S2 is connected in parallel to both ends of the first resistor R2; the other end of the second resistor R3 is connected to one end of the third switch S3, and the other end of the third switch S3 is connected to the negative power supply pin GND.

[0080] It can be understood that the sampling unit is a sampling unit that is originally external and used to form demagnetization detection and is now built into the chip, and is combined with the second switch S2 and the third switch S3 to form a sampling control module 130. For example, the first switch S1, the second switch S2 and the third switch S3 can all be implemented by switching devices such as triodes, MOS tubes, etc.

[0081] In addition, the sampling control module 130 is also used to control the short circuit state between the first end and the second end of the sampling control module 130 to be disconnected and the second end and the third end to be connected when the main switch tube Q1 is turned off after the second end of the sampling control module 130 is disconnected from the positive power supply pin VDD. And, after the main switch tube Q1 is turned off, the sampling control module 130 is also used to collect the electrical signal on the demagnetization detection pin DEM through the sampling unit, that is, to sample the voltage or current signal on the auxiliary winding, so as to judge the state of the transformer T according to the electrical signal, for example, whether it has entered the demagnetization stage, whether the demagnetization is completed, and whether it has entered the quasi-resonance period.

[0082] Furthermore, when it is detected that the demagnetization of the transformer T is completed, the sampling unit is also used to obtain the resonant current of the transformer T in the resonance (QR) stage. Then, the power control chip U1 controls the main switch tube Q1 to turn on when the resonant current is zero according to the size of the resonant current, so as to reduce the switching loss of the main switch tube Q1.

[0083] Different from the conventional flyback converter, the main winding and the auxiliary winding of this embodiment have the same polarity. Figure 3As shown, the opposite-name end of the main winding is used to connect the input voltage, and the same-name end is connected to the main switch tube Q1; the opposite-name end of the auxiliary winding is connected to the demagnetization detection pin DEM of the power control chip U1, and the same-name end is grounded. This design allows the auxiliary winding to supply power when the main switch tube Q1 is turned on, instead of adopting the traditional power supply solution during demagnetization. In this way, the power supply voltage of the chip no longer changes within the range of 6 times the output voltage, but only follows the change of the input voltage. Usually, the input voltage range is 90V~264V, which is roughly about 3 times. As long as a reasonable turns ratio is set, when the input voltage is 264V, the reflected voltage of the auxiliary winding is about 40V. Then when the input is 90V, the charging voltage is 13V, which can also meet the minimum voltage required for the energy efficiency of the main switch tube Q1.

[0084] Further, as Figure 3 Taking the flyback power converter shown as an example, the transformer T in the power converter 100 includes a secondary winding with opposite polarity to the main winding, and the power converter 100 also includes: a rectifier diode D2 and an output capacitor C2, wherein the same-name end of the secondary winding is connected to the positive electrode of the output capacitor C2 through the forward-set rectifier diode D2, and the opposite-name end is connected to the negative electrode of the output capacitor C2, and then, the two ends of the output capacitor C2 are used to connect the load and power the load.

[0085] The power converter 100 of this embodiment can well overcome the defect in the prior art that the power supply voltage of the power control chip U1 needs to withstand a higher voltage due to the voltage following of the conventional auxiliary winding by setting the auxiliary winding and the main winding to have the same polarity. In addition, this embodiment uses the internal design of the power control chip U1 to realize the circuit structure of internal charging. Whether during the conduction period or the shutdown period of the main switch tube Q1, the voltage of the chip can be stabilized at the required value. By abandoning the traditional LDO and the circuit structure with high loss such as resistor current limiting, the chip can work at a reasonable and stable working voltage, thereby reducing the loss, improving the efficiency, reducing the stress of the switch tube, and improving the electromagnetic interference (EMI). In addition, no additional LDO or other devices are required in the periphery, so as to achieve the purpose of green energy saving and environmental protection.

[0086] Example 2

[0087] Please refer to Figure 3 and 5 Based on the power converter 100 of the above-mentioned embodiment 1, this embodiment proposes a power supply control method of the power converter 100, which can be used to realize the self-starting and self-power supply control of the power converter 100.

[0088] Exemplarily, when the power converter 100 is powered on, that is, when the power converter 100 is connected to a high voltage, since the main switch tube Q1 has no signal, no current flows through the coil of the transformer T, and therefore there is no voltage drop between the coils of each transformer T, the voltage V of the demagnetization detection pin DEM is DEM =0; the voltage V on the positive power supply pin VDD DD A small current flows through the current limiting resistor R1 of the high voltage power supply to charge the power supply capacitor C1. At this time, the chip does not consume power. DD The voltage detection module 110 does not work at this time, so V DD can be stored instead of being discharged by the DEM pin. Then, the voltage V DD It can be slowly increased to the voltage point Vstart that the circuit needs to start. Then, the power control chip U1 starts to enter the working state, thus completing the self-start of the circuit.

[0089] After the power control chip U1 works normally, in order to maintain the chip voltage, the power supply control method exemplarily includes:

[0090] Step S110 , when the voltage detection module 110 detects that the voltage of the positive power pin VDD is lower than a preset value, a path opening signal is generated.

[0091] In step S120 , when the charging control module 120 receives the path opening signal, the second terminal of the sampling control module 130 and the positive power supply pin VDD are controlled to be in a conductive state.

[0092] Exemplarily, when the voltage V DD When it is lower than a set value, a path opening trigger signal is generated to the charging control module 120, and the charging control module 120 will make the second end of the sampling control module 130 and the positive power supply pin VDD in a conductive state, that is, if current is injected into the second end at this time, the inflowing current can automatically turn on the switch tube in the charging control module 120, so that the current can flow to the positive power supply pin VDD through the charging control module 120.

[0093] For example, Figure 4 Taking the power converter 100 as an example, when it is detected that the voltage on the positive power pin VDD meets the requirement, the first switch S1 will receive a path opening signal, so that the first switch S1 is closed, and then the current source is connected to the gate of the switch tube. At this time, the switch tube in the sampling control module 130 is in a state that can be turned on at any time.

[0094] In step S130, when the second terminal of the sampling control module 130 and the positive power supply pin VDD are in a conductive state, when the main switch tube Q1 is turned on, the sampling control module 130 controls the first terminal and the second terminal of the sampling control module 130 to be short-circuited and the second terminal and the third terminal to be open-circuited, so that the current generated by the auxiliary winding flows from the demagnetization detection pin DEM to the power supply capacitor C1.

[0095] Exemplarily, when the first switch S1 is closed, when the main switch tube Q1 is turned on, the first terminal and the second terminal of the sampling control module 130 are short-circuited and the second terminal and the third terminal are open-circuited, that is, the second switch S2 is turned on and the third switch S3 is turned off. At this time, the voltage of the auxiliary winding rises Vaux=Vin / Np*Na. The current source I1 passes through the first switch S1 and forms a voltage drop V on the voltage drop resistor R5. fall =I1*R1, set this voltage drop value greater than the absolute value of the switch tube's turn-on voltage Vth. At this time, the first switch tube Q0 is turned on, and the current generated on the auxiliary winding will flow from the second switch S2, through the first switch tube Q0, and then through the clamping diode D1, and finally charge the power supply capacitor C1 through the pin VDD.

[0096] Then, the voltage detection module 110 starts to work. DD When the voltage rises slowly to the set value, the voltage detection module 110 will generate a path disconnection signal, and the first switch S1 is disconnected. When the main switch conduction signal Ton comes, the second switch S2 is controlled to close and the third switch S3 is disconnected. At this time, the DEM pin is pulled up by the inductive voltage on the auxiliary winding. Since the first switch S1 is disconnected, no voltage drop can be generated on the voltage drop resistor R5. At this time, the switch tube is closed, and the DEM pin cannot charge the power supply capacitor C1, so that the voltage of the pin VDD is clamped at the set value.

[0097] Furthermore, the power supply control method further includes: when it is detected that the voltage of the positive power supply pin VDD is higher than a preset value, a path shutoff signal is generated. At this time, when the charging control module 120 receives the path shutoff signal, the conductive state between the second end of the sampling control module 130 and the positive power supply pin VDD is disconnected.

[0098] The power supply control method further includes: when the conductive state between the second end of the sampling control module 130 and the positive power supply pin VDD is disconnected, when the main switch tube Q1 is turned off, the sampling control module 130 controls the short circuit state between the first end and the second end of the sampling control module 130 to be disconnected and the second end and the third end to be conductive.

[0099] Exemplarily, when the main switch Q1 is turned off, the transformer T begins to enter the demagnetization stage, the third switch S3 is closed, the second switch S2 is turned off, and the first switch S1 is also in the off state. At this time, the auxiliary winding voltage is -Vout / Ns*NA. The voltage V on the DEM pin is DEM =-Vout / Ns*NA. Since the clamping diode D1 is in a reverse biased state, the current of the power supply capacitor C1 is blocked from being consumed.

[0100] Furthermore, the sampling control module 130 includes a second switch S2, a third switch S3, and a sampling unit composed of a first resistor R2 and a second resistor R3 connected in series. Therefore, after the main switch tube Q1 is turned off, the power supply control method further includes: collecting an electrical signal on the demagnetization detection pin DEM through the sampling unit to determine the state of the transformer T, and after the demagnetization of the transformer T is completed, obtaining the resonant current of the transformer T in the resonant stage, wherein the resonant current is used to control the main switch tube Q1 to turn on when the resonant current is zero.

[0101] Exemplarily, when the transformer T is demagnetized, the inductance of the main winding and the parasitic capacitance of the main switch tube Q1 form an LC resonance, the resonance amplitude of the auxiliary winding is 2Vout / Ns*NA, the intermediate voltage is 0V, and the third switch S3 is closed, and the second switch S2 and the first switch S1 are both in the open state. When the voltage is positive, the positive pin VDD of the power supply will not be charged, and when the voltage is negative, D2 will not release current due to reverse bias. At this time, by detecting the electrical signal of the DEM pin, when it is detected that the resonant current on the main winding is 0, the main switch tube Q1 can be controlled to be turned on again. It can be seen from the above that the power supply circuit scheme of this embodiment will not affect the existing QR detection, that is, the chip voltage is stabilized and clamped without affecting the existing functions.

[0102] It can be understood that the options in the above-mentioned embodiment 1 are also applicable to the power converter 100 in this embodiment, so they will not be described repeatedly here.

[0103] Example 3

[0104] Please refer to Figure 6 , the embodiment of the present application also provides a power control chip U1, which can be used in the power converter 100 operating in the quasi-resonant mode. Exemplarily, the power control chip U1 includes: a demagnetization detection pin DEM, a positive power pin VDD, a negative power pin GND and a built-in charging control module 120, and may also include a built-in sampling control module 130 and a voltage detection module 110. In some embodiments, the sampling control module 130 and the voltage detection module 110 can be used as peripheral circuits of the power control chip U1, and their positions are not limited.

[0105] Among them, the demagnetization detection pin DEM is used to connect the auxiliary winding of the transformer T in the converter; the positive power supply pin VDD is used to be grounded through the power supply capacitor C1, and is also connected to the main winding of the transformer T via the current limiting resistor R1; the negative power supply pin GND is used for grounding; among them, the polarity of the auxiliary winding is the same as that of the main winding, and the main winding is used to connect the main switch tube Q1.

[0106] The first end of the sampling control module 130 is connected to the demagnetization detection pin DEM, the second end is connected to the first end of the charging control module 120, and the third end is connected to the negative power supply pin GND; the second end of the charging control module 120 is connected to the output end of the voltage detection module 110, and the third end is connected to the positive power supply pin VDD. The input end of the voltage detection module 110 is connected to the positive power supply pin VDD.

[0107] The voltage detection module 110 is used to detect the voltage of the positive power pin VDD, and output a path-on signal when the voltage of the positive power pin VDD is lower than a preset value; the charging control module 120 is used to control the second end of the sampling control module 130 and the positive power pin VDD to be in a conductive state when receiving the path-on signal; the sampling control module 130 is used to control the first end and the second end of the sampling control module 130 to be short-circuited and the second end and the third end to be open-circuited after the second end of the sampling control module 130 and the positive power pin VDD are in a conductive state when the main switch tube Q1 is turned on, so that the current generated by the auxiliary winding flows from the demagnetization detection pin DEM to the power supply capacitor C1.

[0108] It can be understood that the options regarding the power control chip in the above-mentioned embodiment 1 are also applicable to this embodiment, so they are not repeatedly described here.

[0109] The present application also provides an electronic device. Exemplarily, the electronic device includes the power converter in the above-mentioned embodiment 1, wherein the power converter can perform circuit self-starting and stabilize the power supply voltage of the power control chip according to the power supply control method in embodiment 2.

[0110] The above description is only a specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application.

Claims

1. A power converter, characterized in that: include: A transformer, a main switch tube, a power control chip, a power supply capacitor, a current limiting resistor, a voltage detection module and a sampling control module, wherein the transformer includes a main winding and an auxiliary winding with the same polarity, the power control chip includes a demagnetization detection pin, a positive power pin, a negative power pin and a charging control module, and the sampling control module and the voltage detection module are located inside or outside the power control chip; The first end of the main winding is used to connect to the input voltage, and the second end is connected to the main switch tube; A first end of the auxiliary winding is connected to the demagnetization detection pin, and a second end is grounded; The positive pin of the power supply is grounded through the power supply capacitor and is also connected to the first end of the main winding via the current limiting resistor; the negative pin of the power supply is grounded; The first end of the sampling control module is connected to the demagnetization detection pin, the second end is connected to the first end of the charging control module, and the third end is connected to the negative power pin; The second end of the charging control module is connected to the output end of the voltage detection module, and the third end is connected to the positive electrode pin of the power supply; The input end of the voltage detection module is connected to the positive pin of the power supply.

2. The power converter according to claim 1, characterized in that: The voltage detection module is used to detect the voltage of the positive pin of the power supply, and output a path opening signal when the voltage of the positive pin of the power supply is lower than a preset value; The charging control module is used to control the second end of the sampling control module and the positive pin of the power supply to be in a conductive state when receiving the path opening signal; Wherein, the charging control module includes a switch unit and a clamping diode, the first end of the switch unit is connected to the second end of the sampling control module, the second end is connected to the clamping diode set in the forward direction, and the third end is connected to the output end of the voltage detection module.

3. The power converter according to claim 2, characterized in that: The switch unit includes a current source, a voltage drop resistor, a first switch tube and a first switch, the voltage drop resistor is connected in parallel between the control end and the first end of the first switch tube, the first end of the first switch tube is connected to the second end of the sampling control module, the second end is connected to the clamping diode, and the control end is connected to the first end of the first switch; The second end of the first switch is connected to the current source, and the control end is connected to the voltage detection module.

4. The power converter according to claim 3, characterized in that: The first switch tube is a MOS tube or a triode.

5. The power converter according to any one of claims 1 to 4, characterized in that: The sampling control module is used to control the short circuit between the first end and the second end of the sampling control module and the open circuit between the second end and the third end when the main switch tube is turned on after the second end of the sampling control module and the positive pin of the power supply are in a conductive state, so that the current generated by the auxiliary winding flows from the demagnetization detection pin to the power supply capacitor; Wherein, the sampling control module includes a second switch, a third switch and a voltage dividing unit composed of a first resistor and a second resistor connected in series; One end of the first resistor is connected to the demagnetization detection pin, and the other end is respectively connected to one end of the second resistor and the first end of the charging control module; The second switch is connected in parallel to two ends of the first resistor; The other end of the second resistor is connected to one end of the third switch, and the other end of the third switch is connected to the negative power supply pin.

6. A power supply control method for a power converter, characterized in that: The power converter is the power converter as claimed in claim 1, and the method comprises: When it is detected that the voltage of the positive pin of the power supply is lower than a preset value, a path opening signal is generated; When the charging control module receives the path opening signal, the second end of the sampling control module and the positive pin of the power supply are controlled to be in a conductive state; When the second end of the sampling control module and the positive power supply pin are in a conductive state, when the main switch tube is turned on, the sampling control module controls the first end and the second end of the sampling control module to be short-circuited and the second end and the third end to be open-circuited, so that the current generated by the auxiliary winding flows from the demagnetization detection pin to the power supply capacitor.

7. The power supply control method of the power converter according to claim 6, characterized in that: Also includes: When it is detected that the voltage of the positive pin of the power supply is higher than the preset value, a path shutoff signal is generated; When receiving the path shutoff signal, the charging control module controls the conductive state between the second end of the sampling control module and the positive pin of the power supply to be disconnected.

8. The power supply control method of the power converter according to claim 7, characterized in that: Also includes: After the conductive state between the second end of the sampling control module and the positive power supply pin is disconnected, when the main switch tube is turned off, the sampling control module controls the short circuit state between the first end and the second end of the sampling control module to be disconnected and the second end and the third end to be conductive.

9. The power supply control method of a power converter according to any one of claims 6 to 8, characterized in that: The sampling control module includes a second switch, a third switch, and a sampling unit composed of a first resistor and a second resistor connected in series, wherein one end of the first resistor is connected to the demagnetization detection pin, and the other end is respectively connected to one end of the second resistor and the first end of the charging control module; The second switch is connected in parallel to both ends of the first resistor; the other end of the second resistor is connected to one end of the third switch, and the other end of the third switch is connected to the negative electrode pin of the power supply; The method further comprises: The sampling unit collects the electrical signal on the demagnetization detection pin to determine the state of the transformer. After the transformer is demagnetized, the resonant current of the transformer in the resonant stage is obtained. The resonant current is used to control the main switch tube to turn on when the resonant current is zero.

10. A power control chip, characterized in that: include: Demagnetization detection pin, positive power pin, negative power pin, sampling control module, charging control module and voltage detection module; The demagnetization detection pin is used to connect the auxiliary winding of the transformer in the power converter; The positive power supply pin is used to be grounded through a power supply capacitor and is also connected to the main winding of the transformer via a current limiting resistor; the negative power supply pin is used to be grounded; wherein the auxiliary winding has the same polarity as the main winding, and the main winding is connected to the main switch tube in the power converter; The first end of the sampling control module is connected to the demagnetization detection pin, the second end is connected to the first end of the charging control module, and the third end is connected to the negative power pin; The second end of the charging control module is connected to the output end of the voltage detection module, and the third end is connected to the positive electrode pin of the power supply; The input end of the voltage detection module is connected to the positive pin of the power supply.

Images